End plate, filter element, filter system and method for filtering liquid

ABSTRACT

An end plate for filter material for filtering a liquid, particularly a hydraulic oil, having a through opening for filtered liquid, which is surrounded by a sealing ring for a connecting piece, and a cover for the filter material. The sealing ring delimits a free space for accommodating an anti-rotation lock of a switch and/or a bypass valve of a filter system. Furthermore, a filter element, a filter system and a method for filtering liquid are also disclosed.

The invention relates to an end plate for filter material for filteringa liquid, particularly a hydraulic oil with the features of the preambleof claim 1. An end plate of this type is known for example from DE 102013 106 264 A1. The invention further relates to a filter element forfiltering a liquid, a filter system and a method for filtering liquid.

Hydraulic systems are used for example in construction machines,agricultural machines, machine tools or processing machines. Thehydraulic oil used in hydraulic systems is usually filtered. The filterelements used for this absorb the dirt particles from the hydraulic oiland must be replaced after a certain time.

In this context, DE 10 2013 106 264 A1 describes a filter element forfiltering a liquid, with an end plate, which is divided into two partsand has a fixed and a movable plate part, as a result of which thereplacement of the filter element is facilitated. A further filterelement is known from EP 2 092 970 A1. The known filter elements do notmake it possible to automatically determine the degree of contaminationof the filter material.

The invention is based on the object of specifying an end plate forfilter material, for filtering a liquid, which allows the use of acontamination indicator and/or a bypass valve in a filter element or afilter system with such a filter element. The invention is further basedon the object of specifying a filter element, a filter system and amethod for filtering liquid.

According to the invention, the object is achieved with regards to theend plate by means of the subject matter of claim 1. With regards to thefilter element, the filter system and the method for filtering liquid,the object is achieved according to the invention by means of thesubjects of claims 9, 11 and 14.

The invention is based on the idea of specifying an end plate for filtermaterial for filtering a liquid, particularly a hydraulic oil, having athrough opening for filtered liquid, which is surrounded by a sealingring (20) for a connecting piece, and a cover for the filter material.The sealing ring delimits a free space for accommodating ananti-rotation lock of a switch and/or bypass valve of a filter system.

The invention has the advantage that the anti-rotation lock moves infree space during the actuation of the switch and/or the bypass valve,i.e. can be moved into the free space or out of the free space. Theanti-rotation lock is used to guide the switch and/or the bypass valvein a predetermined position in the filter head, so that for example anoptimum flow behaviour of the bypass valve or the optimum position ofthe switching components of the switch is achieved during mounting andduring operation. The bypass valve and/or the switch require a minimumtravel for actuation and correct mode of action. The free space of theend plate according to the invention means that the anti-rotation lockis effective over the entire travel without the anti-rotation lockcolliding with the end plate. In the maximum position, for example inthe rest position of the switch and/or the bypass valve, theanti-rotation lock can on the one hand dip completely into the freespace of the end plate. On the other hand, a sufficiently largeadjustment path is available for actuating the switch and/or the bypassvalve, in which the anti-rotation lock guides or holds the switch and/orthe bypass valve in the desired position.

The delimiting of the free space by the sealing ring provides the designprerequisite for making the filter system compact, because theanti-rotation lock can be arranged in the vicinity of the sealing ring,specifically on the sealing ring. This means that the anti-rotation lockcan be arranged close to the through opening in the mounted state. Thesealing ring forms the inner wall of the free space and seals againstthe outlet connection in the mounted state.

The sealing ring is preferably constructed in one piece with the endplate.

Therefore, the end plate according to the invention makes it possiblenot only to equip a filter system with a switch and/or a bypass valve,but even to use a switch and/or bypass valve, which require aparticularly large travel. The switch can be used in order to indicate aparticular degree of contamination of the filter element. Instead of theswitch or in addition to the switch, the end plate can be used with abypass valve, which allows a safety function, for example switching offthe filter function, when a particular degree of contamination isreached.

The end plate is marketable as such and is therefore disclosed andclaimed independently of the filter element. In addition, the end plateis disclosed and claimed in connection with the filter element. The endplate forms part of the filter element.

In the installed state, the end plate functions as the interface of thefilter element to the filter system, in which the filter element isused. In this case, the end plate is used on the one hand to transferthe filtered liquid into the filter head of the filter system. On theother hand, the end plate is used to enable the switch function orbypass functions of the filter head. To this end, the free space for theanti-rotation lock according to the invention is provided in the endplate. The anti-rotation lock as such does not form part of the endplate but interacts with the same in the installed state. Theanti-rotation lock is part of the filter head or the componentsintegrated into the filter head, specifically of the switch and/or thebypass valve.

Preferred embodiments of the invention are indicated in the dependentclaims.

In a preferred embodiment, the free space is constructed as anaccommodating pocket, which extends between the sealing ring and thecover and has a base. The anti-rotation lock is arranged in the freespace between the sealing ring and the cover. This embodiment has theadvantage that a structurally beneficial movement direction of theswitch and/or the bypass valve, specifically in the axial direction ofthe filter element or along the flow direction of the liquid, ispossible due to the end plate. The invention is not limited to endplates through which axial flow is possible. Other geometries of the endplate are possible. The accommodating pocket has the further advantagethat the accommodating pocket has a base, so that the filter spaceadjoining the end plate is sealed.

The accommodating pocket is preferably of annular construction. On theone hand, this has the advantage in terms of production technology, thatthe end plate can for example be constructed as an injection-mouldedpart with flow paths of virtually equal length. On the other hand, theend plate is simple to mount, as it is not necessary to align the endplate relatively to the anti-rotation lock.

In a further preferred embodiment, the cover has an inner ring, whereinthe accommodating pocket is constructed between the sealing ring and theinner ring. The inner ring allows an optimal utilization of the overallheight of the filter element, as the axial end of the filter materialcan be arranged in the region of the inner ring and therefore higherthan the base of the accommodating pocket, particularly at the sameheight as the accommodating pocket.

The height position of the base or of the axial end of the filtermaterial relates to the longitudinal extent of the filter element.

The inner ring may form a positioning ring for a support tube andconsequently has a dual function, as the inner ring forms the outer wallof the free space or the accommodating pocket and positions the supporttube. Also, in this embodiment, the inner ring is constructed in onepiece with the end plate.

In a particularly preferred embodiment, the free space has a depth inthe axial direction with respect to the longitudinal extent of thesealing ring, which at least corresponds to the penetration depth of theanti-rotation lock into the free space. Penetration depth is understoodto be the distance by which the anti-rotation lock is moved into thefree space. This embodiment is advantageous in connection with theaccommodating pocket in particular, because in this manner, theanti-rotation lock is reliably prevented from colliding with the base ofthe end plate.

Preferably, the sealing ring has an upper edge, wherein the depth is atleast 5 mm, particularly at least 10 mm, in particular at least 15 mmfrom the upper edge of the sealing ring. Thus, a sufficiently longadjustment path is available for the anti-rotation lock.

Furthermore, the free space, the accommodating pocket in particular,preferably has a width in the radial direction starting from the sealingring, which is at least 2 mm. This has the advantage that theanti-rotation lock can be constructed in a sufficiently stable manner.

With regards to the advantages of the filter element and the filtersystem, reference is made to the statements in connection with the endplate.

In the case of the filter system, one advantageous embodiment is thatthe bypass valve, in the switched state, connects the inlet side of thefilter head and the outlet side of the filter head. This has theadvantage that emergency operation of the filter system is possible ifthe filter material has reached a certain degree of contamination. Inthis case, it is accepted that the filter function is at least limited,specifically at most until the filter material is replaced.

A further advantageous embodiment of the filter system is that theswitch comprises a reed contact for generating a signal for acontamination indicator. Reed contacts are known as hermetically sealedswitches which are actuated by means of an external magnetic field andare very suitable for use in a hydraulic filter system. Accordingly, theswitch comprises a magnetic element which interacts with the reedcontact. The invention is not limited to certain reed contact types.

In the context of the method according to the invention, it is providedthat liquid to be filtered is supplied to a filter system according tothe invention, filtered in the filter material and discharged throughthe through opening of the end plate as filtered liquid. The switchand/or the bypass valve are actuated from a differential limit pressurebetween the liquid to be filtered and the filtered liquid. As a result,the degree of contamination can be indicated and/or emergency operationof the filter system can be initiated.

The invention is explained in more detail in the following with furtherdetails and with reference to the attached schematic drawings on thebasis of an exemplary embodiment.

In the figures

FIG. 1 shows the section of a filter system with a filter element and anend plate according to an exemplary embodiment according to theinvention, and

FIG. 2 shows a detail view of the filter system according to FIG. 1 inthe region of the end plate.

FIG. 1 shows a filter system 30 for use in a hydraulic system, forexample for a construction machine, agricultural machine, machine toolor processing machine. The filter system 30 is generally suitable forhydraulic systems in which hydraulic fluid, particularly hydraulic oilmust be filtered.

The filter system 30 has a filter head 27 with a first connection 28 anda second connection 29. Hydraulic fluid to be filtered enters the filtersystem through the first connection 28 during the use of the filtersystem 30. The filtered hydraulic fluid exits the filter system 30through the second connection 29. The filter head 27 is connected in asealed manner, for example screwed, to a filter housing 26. A filterelement 25 is arranged in the filter housing 26. The filter element 25comprises a filter material 10, which effects the filter function duringoperation. The invention is not limited to certain filter materials.Preferably, the filter material 10 is constructed from layers folded ina star-shaped manner. The superordinate contour or outer contour of thefilter material 10 is cylindrical. In other words, the macroscopic shapeof the filter material 10 is cylindrical and the microscopic shape ofthe filter material 10 is star-shaped. The inner wall of the cylindricalfilter material 10 bears against a support tube 23, which has throughopenings 31 for the hydraulic fluid arranged in the longitudinaldirection and in a distributed manner on the circumference. The supporttube 23 supports the filter material 10 in the radial direction.

In the axial direction, the filter element 25 is delimited by two endplates 24, 32. The two end plates 24, 32 bear against the end faces ofthe filter material 10. The end plates 24, 32, the support tube 23 andthe filter material together form the filter element 25, which can behandled and marketed as one unit. The filter element 25 forms a wearingpart, which is replaced as a whole when the filter material 10 iscontaminated.

The end plate 32, which is arranged at the bottom in the installationdirection of the filter element 25, is closed and seals the interior ofthe support tube 23 and the filter material 10 in the filter housing 26downwards. The end plate 24, which is arranged at the top in theinstallation direction of the filter element 25, has a through opening11, through which the filtered hydraulic oil or, in general, thefiltered hydraulic fluid exits the filter element 25. The throughopening 11 is arranged centrally in the end plate 24, i.e. in themiddle. It is also conceivable that the through opening 11 is arrangedeccentrically. In the example according to FIG. 1, the filter material10, the support tube 23 and the through opening 11 are arrangedcoaxially. A different arrangement of these components is possible.

The upper end plate 24 furthermore has a cover 12, against which, in theinstalled state, the filter material 10, specifically the end face ofthe filter material 10 bears. The cover 12 has an annular disc 43, whichis arranged coaxially to the through opening 11. The cover furthermorehas an inner ring 21 and an outer ring 33, which are connected to theannular disc 43 in each case. The inner ring 43 and the outer ring 33are arranged coaxially and, with the disc 43, form an annular receptaclefor the axial end of the filter material 10. The inner ring 21 and theouter ring 33 overlap the filter material 10 at least to some extent.

A plurality of spacers 34 are arranged at the outer ring 33, for examplein the form of lugs, which position the filter element 25 in the housingin the filter housing 26 in such a manner that an annular gap is formedbetween the filter material 10 and the inside of the filter housing 26.

Other geometries of the end plate 24 are possible.

During operation, the hydraulic oil to be filtered flows through thefirst connection 28 into the filter head 27 and from there radiallyoutwards, past the upper end plate 24 into an annular gap between thefilter element 25 and the filter housing 26. From there, the hydraulicoil flows through the filter material 10 in the radial direction, flowsthrough the support tube 23 and from there is conveyed in the cleanedstate through the through opening 11 back into the filter head 27 again.There, the cleaned hydraulic oil exits through the second connection 29.

The upper end plate 24 is illustrated enlarged in FIG. 2.

There it can be seen that a free space 13 is formed between the throughopening 11 and the cover 12, specifically the inner ring 21 of the cover12, which, in the installed state, accommodates an anti-rotation lock 14of a switch 15 and/or a bypass valve 16 of the filter head 27. Theanti-rotation lock 14 is constructed in the example according to FIG. 2as a pin-shaped projection or protrusion of the switch 15 or the bypassvalve 16. The anti-rotation lock 14 protrudes in the installed stateover the disc 43 of the cover 12 in the axial direction of the filterelement 25. The anti-rotation lock 14 and the free space 13 are flush inthe axial direction, so that the anti-rotation lock 14 can dip into thefree space 13 when the switch 15 or the bypass valve 16 is in the restposition illustrated in FIG. 2. To this end, the depth of the free space13, i.e. the extent of the free space 13 in the axial direction of thefilter element 25 is dimensioned such that the anti-rotation lock 14 canbe moved into the free space 13 completely without colliding with theend plate 24. Specifically, the section of the anti-rotation lock 14,which protrudes in the axial direction over the cover 12 or projectsinto the filter element 25, is accommodated in the free space 13completely.

The free space 13 is constructed as an accommodating pocket 17, whichextends parallel to the flow direction of the liquid through the throughopening 11. In other words, the accommodating pocket 17 extends in theaxial direction of the filter element 25. The accommodating pocket 17has a base 19, which downwardly delimits the accommodating pocket 17,i.e. delimits and seals towards the interior of the support tube 23.This means that the cleaned liquid exits entirely through the throughopening 11 and the dirty side is separated from the clean side of thefilter system 30. The accommodating pocket 17 is of annularconstruction, so that during the mounting of the end plate, it is notnecessary to determine the position thereof in the circumferentialdirection with respect to the anti-rotation lock 14.

The sealing ring 20 and the inner ring 21 are arranged coaxially andextend in the longitudinal direction of the filter element 25. Thesealing ring 20 adjoins the through opening 11 and is used on the onehand to accommodate and seal a connecting piece 22 of the filter head27. On the other hand, the sealing ring 20 forms the inner wall of theaccommodating pocket 17. The inner ring 21 adjoins the annular disc 43of the cover 12 and extends substantially parallel to the sealing ring20. The inner ring 21 is used to position the support tube 23 at leastduring mounting. In addition, the inner ring 21 forms the outer wall ofthe accommodating pocket 17.

The accommodating pocket 17 can also be understood as the annular gapbetween the cover 12 and the through opening 11, which annular gap isclosed at the bottom, i.e. in the direction of the lower end plate 32.

On the side of the end plate 24 facing away from the connecting piece22, a plurality of axial ribs 35 are arranged on the circumference ofthe through opening 11, which axial ribs extend into the interior of thesupport tube 23 in the installed state.

As can be seen further in FIG. 2, the filter head 27 has a switch andvalve unit 36, which comprises a switch 15 and a bypass valve 16 as anintegrated component. It is also possible to construct the switch 15 andthe bypass valve 16 as separate components with their own anti-rotationlock 14 in each case. The accommodating pocket 17 can accommodate aplurality of anti-rotation locks in a distributed manner on thecircumference. It is also possible to provide only one switch 15 or onlyone bypass valve 16 in the filter head 27.

In the example according to FIG. 2, the anti-rotation lock 14 isarranged as a pin-shaped projection or protrusion on a valve body 37 ofthe bypass valve 16. The anti-rotation lock 14 and the valve body 37 arepreferably constructed in one piece. The valve body 37 is constructedcylindrically. The anti-rotation lock 14 is arranged eccentrically withrespect to the valve body 37, specifically on the circumference of thevalve body 37. This has the advantage that the anti-rotation lock 14 canbe arranged close to the through opening 11.

The valve body 37 has a piston 18, which is guided in a slidable mannerin the filter head 27.

The bypass valve 16, specifically the valve body 37, has a plurality offlow openings, which are arranged in a distributed manner on thecircumference of the bypass valve 16 or the valve body 37. In the reststate according to FIG. 2, the flow openings are closed, so that theclean side and the dirty side of the filter system 30 are separated.

The bypass valve 16 has an axial guide 38, for example in the form ofguide ribs, which encompass a coaxially arranged pin 39 of the switch15. The pin 39 is connected to a switch component 40, which is mountedsecurely in the filter housing 27 and which contains the electronics ofthe switch 15. The axial guide 38 of the bypass valve 16 is connected toa magnetic element 41, which can be moved on the pin 39 in the axialdirection together with the bypass valve 16, when a correspondingdifferential limit pressure is reached. As a result, the switch 15 isactuated. A spring 42 is arranged between the valve body 37 and thefixedly arranged switch component 40, which spring ensures that thebypass valve 16 and the switch 15 remain in the rest position until thedifferential limit pressure is reached at a certain degree ofcontamination of the filter element 25. The reed contact itself can beopen or closed in the rest position.

The anti-rotation lock 14 blocks a movement in the circumferentialdirection of the valve body 37 or in general of the bypass valve 16, sothat the valve body 37 can essentially only be moved in the axialdirection of the filter element 25. To this end, the anti-rotation lock14 is in engagement with the filter head, for example by means of acorresponding groove in the filter head 27.

As the anti-rotation lock 14 protrudes in the direction of the filterelement 25 over the valve body 37, it is achieved that the anti-rotationlock 14 remains in engagement with the filter housing 27, even if thebypass valve 16 or the switch 15 are actuated. Different switchingpoints of the bypass valve 16 and the switch 15 can be set by means ofthe length of the anti-rotation lock 14. For example, the switch 15 mayswitch already at a lower differential limit pressure than the bypassvalve 16 or vice versa.

The filter system according to FIGS. 1 and 2 functions as follows duringuse.

Hydraulic oil to be filtered is supplied to the filter element 25through the first connection 28, which hydraulic oil flows through thefilter material 10 in the radial direction. From the interior of thesupport pipe 23, the cleaned hydraulic oil passes through the throughopening 11 back into the filter head 27 and from there through thesecond connection 29 back into the hydraulic system. With an increasingdegree of contamination of the filter material 10, the back pressure inthe region of the first connection 28 increases, which connection isfluidly connected via an annular space to the bypass valve, so that thebypass valve 16 is loaded with the corresponding pressure. When thedifferential pressure consequently created between the dirty side andthe clean side of the filter system 30 exceeds a certain limit value,which results from the spring force of the spring, the bypass valve 16is actuated, i.e. moved out of the rest position. In this case, theanti-rotation lock 14 is also moved in the axial direction, whichremains in engagement with the filter housing 27 during the travellingmovement of the bypass valve 16 and thus positions the bypass valve 16and the switch 15 in the circumferential direction. The magnetic element41 is entrained in the process, so that the switch 15 is actuated andindicates the degree of contamination. If the degree of contaminationincreases further, the bypass valve 16 is switched, so that the flowopenings in the bypass valve 16 are enabled and the clean side isconnected to the dirty side, bypassing the filter element 25 (bypass).

As soon as the contaminated filter element 25 has been replaced with anew filter element 25, the back pressure drops and the bypass valve andthe switch 15 return to the rest position. In this case, theanti-rotation Lock 14 again dips into the free space 13 of the end plate24.

REFERENCE LIST

-   10 Filter material-   11 Through opening-   12 Cover-   13 Free space-   14 Anti-rotation lock-   15 Switch-   16 Bypass valve-   17 Accommodating pocket-   18 Piston-   19 Base-   20 Sealing ring-   21 Inner ring-   22 Connecting piece-   23 Support tube-   24 (Upper) end plate-   25 Filter element-   26 Filter housing-   27 Filter head-   28 First connection-   29 Second connection-   30 Filter system-   31 Through openings-   32 (Lower) end plate-   33 Outer ring-   34 Spacer-   35 Axial ribs-   36 Switch and valve unit-   37 Valve body-   38 Axial guide-   39 Pin-   40 Switch component-   41 Magnetic element-   42 Spring-   43 Disc

1. An end plate for filter material for filtering a liquid, particularlya hydraulic oil, having a through opening for filtered liquid, which issurrounded by a sealing ring for a connecting piece, and a cover for thefilter material, wherein the sealing ring delimits a free space foraccommodating an anti-rotation lock a switch and/or a bypass valve of afilter system.
 2. The end plate according to claim 1, wherein the freespace forms an accommodating pocket, which extends between the sealingring and the cover and has a base.
 3. The end plate according to claim1, wherein the annular space, the accommodating pocket in particular, isof annular construction.
 4. The end plate according to claim 1, whereinthe cover has an inner ring, wherein the accommodating pocket isconstructed between the sealing ring and the inner ring.
 5. The endplate according to claim 4, wherein the inner ring forms a positioningring for a support tube.
 6. The end plate according to claim 1, whereinthe free space has a depth in the axial direction with respect to thelongitudinal extent of the sealing ring, which at least corresponds tothe penetration depth of the anti-rotation lock.
 7. The end plateaccording to claim 6, wherein the sealing ring has an upper edge,wherein the depth of the free space is at least 5 mm, particularly atleast 10 mm, in particular at least 15 mm from the upper edge of thesealing ring.
 8. The end plate according to claim 1, wherein the freespace has a width in the radial direction starting from the sealingring, which is at least 2 mm.
 9. A filter element for filtering aliquid, having an end plate according to claim 1 and a filter materialwhich is arranged on the cover and surrounds the through opening at thecircumference thereof.
 10. The filter element according to claim 9,wherein a support tube is arranged on the inner side of the filtermaterial and connected to the end plate.
 11. A filter system having afilter element according to claim 9, a filter housing, in which thefilter element is arranged, and a filter head with connections, which isconnected to the filter housing, wherein the filter head has ananti-rotation lock, which is connected to a switch and/or a bypassvalve, wherein the filter head and the free space of the end plate forman interface.
 12. The filter system according to claim 11, wherein thebypass valve in the switched state connects the inlet side of the filterhead and the outlet side of the filter head.
 13. The filter systemaccording to claim 11, wherein the switch comprises a reed contact forgenerating a signal for a contamination indicator.
 14. A method forfiltering liquid, in which liquid to be filtered is supplied to a filtersystem according to claim 11, filtered in the filter material anddischarged through the through opening of the end plate as filteredliquid, wherein the switch and/or the bypass valve is actuated from adifferential limit pressure between the liquid to be filtered and thefiltered liquid.